package com.example.strategy;

import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
import java.util.concurrent.atomic.AtomicInteger;

import com.alibaba.excel.metadata.Head;
import com.alibaba.excel.write.merge.AbstractMergeStrategy;

import cn.hutool.core.collection.CollUtil;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.util.CellRangeAddress;

/**
 * @author LiYuhang
 * @version 0.1
 * @application
 * @Date 2023/7/20 09:40
 */
public class CustomMergeStrategy extends AbstractMergeStrategy {

    /**
     * 分组，每几行合并一次
     */
    private List<List<Integer>> mergeColDataGroupCountList;

    /**
     * 目标合并列index
     */
    private List<Integer> targetColumnIndex;
    /**
     * 需要开始合并单元格的首行index
     */
    private Integer rowIndex;

    /**
     * mergeColDataList为待合并目标列的值
     */
    public CustomMergeStrategy(List<List<String>> mergeColDataList, List<Integer> targetColumnIndex) {
        this.mergeColDataGroupCountList = getGroupCountList(mergeColDataList);
        this.targetColumnIndex = targetColumnIndex;
    }

    @Override
    protected void merge(Sheet sheet, Cell cell, Head head, Integer relativeRowIndex) {

        if (null == rowIndex) {
            rowIndex = cell.getRowIndex();
        }
        // 仅从首行以及目标列的单元格开始合并，忽略其他
        if (cell.getRowIndex() == rowIndex && targetColumnIndex.contains(cell.getColumnIndex())) {
            //找到对应的需要合并的列
            AtomicInteger i = new AtomicInteger(0);
            Optional<Integer> first = targetColumnIndex.stream().filter(col -> {
                i.getAndIncrement();
                return col == cell.getColumnIndex();
            }).findFirst();
            mergeGroupColumn(sheet, first.get());
        }
    }

    private void mergeGroupColumn(Sheet sheet, Integer index) {
        int rowCount = rowIndex;
        for (Integer count : mergeColDataGroupCountList.get(index)) {
            if (count == 1) {
                rowCount += count;
                continue;
            }
            // 合并单元格
            CellRangeAddress cellRangeAddress = new CellRangeAddress(rowCount, rowCount + count - 1,
                targetColumnIndex.get(index), targetColumnIndex.get(index));
            sheet.addMergedRegion(cellRangeAddress);
            rowCount += count;
        }
    }

    /**
     * 该方法将目标列根据值是否相同连续可合并，存储可合并的行数
     */
    private List<List<Integer>> getGroupCountList(List<List<String>> exportDataList) {
        if (CollUtil.isEmpty(exportDataList)) {
            return new ArrayList<>();
        }
        List<List<Integer>> groupCountListList = new ArrayList<>();
        exportDataList.forEach(dataList -> {
            List<Integer> groupCountList = new ArrayList<>();
            int count = 1;
            for (int i = 1; i < dataList.size(); i++) {
                if (dataList.get(i).equals(dataList.get(i - 1))) {
                    count++;
                } else {
                    groupCountList.add(count);
                    count = 1;
                }
            }
            // 处理完最后一条后
            groupCountList.add(count);
            groupCountListList.add(groupCountList);
        });
        return groupCountListList;
    }
}

